This invention relates to tools, particularly those used in working against hard materials of natural or synthetic origin, e.g., coal, minerals, or concrete pavement, or the like. Such tools are frequently provided with a hard metal carbide tip or insert to better withstand the harsh working surface and provide longer life before replacement becomes necessary. These tools are mounted so as to be freely rotatable in the sockets provided therefor. A typical example of tools of the type to which this invention relates is shown in U.S. Pat. No. Reissue 29,900.
Tungsten carbide working tip inserts have long been known. Sintered tungsten carbide compacted bodies have been found highly useful for cutting, drilling and other tools as well as the production of solid carbide wear parts which are required to be highly resistant to wear as by abrasion and the like, e.g., percussion tools such as coal mining picks, etc.
The volume of mining picks used in this country on an annual basis runs into the tens of millions. A large portion of these picks is provided with a hardened steel shank and a working tip comprising a sintered tungsten carbide insert brazed into a suitable socket at the working end of the tool of the type shown in FIG. 3 of the drawings and identified as "prior art". Under the best operating conditions, the tungsten carbide inserts have a limited life and are subject to rounding off, undercutting wear of the steel body resulting in dislodgment from the socket whereupon the tool wears very rapidly and must be replaced. As a consequence, mining machinery or other machinery utilizing picks is shut-down pending replacement of the picks on the cutter heads.
It is an object of this invention, therefore, to provide an improved working tool especially suited for use as a coal or mineral mining pick, which minimizes the problem of point round off and is capable of operation over a longer period of time than conventional picks before replacement is required.
These and other objects and advantages of the invention which will appear as the description of proceeds, or become evident to those familiar with this art, may be achieved by providing a tool with a self-renewing working tip. As the working tip is worn away by abrasion, impact, loading, corrosion and the like, a renewed working tip is automatically presented as use of the tool is continued.